Recurrent Clostridium difficile diarrhoea.
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Anion Exchange Resins↗
Biomedical subjects
C P Kelly
Publications and source records attributed to C P Kelly.
Asymptomatic carriage of Clostridium difficile and serum levels of IgG antibody against toxin A.
BACKGROUND: Clostridium difficile infection can result in asymptomatic carriage, mild diarrhea, or fulminant pseudomembranous colitis. We studied whether antibody responses to C. difficile toxins affect the risks of colonization, diarrhea, and asymptomatic carriage. METHODS: We prospectively studied C. difficile infections in hospitalized patients who were receiving antibiotics. Serial stool samples were tested for C. difficile colonization by cytotoxin assay and culture. Serum antibody (IgA, IgG, and IgM) levels and fecal antibody (IgA and IgG) levels against C. difficile toxin A, toxin B, and nontoxin antigens were measured by an enzyme-linked immunosorbent assay (ELISA). RESULTS: Of 271 patients, 37 (14 percent) were colonized with C. difficile at the time of admission, 18 of whom were asymptomatic carriers. An additional 47 patients (17 percent) became infected in the hospital, 19 of whom remained asymptomatic. The baseline antibody levels were similar in the patients who later became colonized and those who did not. After colonization, those who became asymptomatic carriers had significantly greater increases in serum levels of IgG antibody against toxin A than did the patients in whom C. difficile diarrhea developed (P<0.001). The adjusted odds ratio for diarrhea was 48.0 (95 percent confidence interval, 3.4 to 678) among patients with colonization who had a serum level of IgG antibody against toxin A of 3.00 ELISA units or less, as compared with patients with colonization who had a level of more than 3.00 ELISA units. CONCLUSIONS: We find no evidence of immune protection against colonization by C. difficile. However, after colonization there is an association between a systemic anamnestic response to toxin A, as evidenced by increased serum levels of IgG antibody against toxin A, and asymptomatic carriage of C. difficile.
Aged↗
Interleukin 16 is up-regulated in Crohn's disease and participates in TNBS colitis in mice.
BACKGROUND & AIMS: Interleukin (IL)-16 is a T lymphocyte- derived cytokine that uses CD4 as its receptor and hence selectively recruits CD4-bearing cells. Infiltrating CD4(+) T cells are a feature of Crohn's disease; however, the role of IL-16 in intestinal inflammation is unknown. The aim of this study was to determine whether IL-16 production is increased in inflammatory bowel disease and whether IL-16 participates in trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice. METHODS: IL-16 messenger RNA and protein levels in inflammatory bowel disease tissues were determined by reverse-transcription polymerase chain reaction and enzyme-linked immunosorbent assay. C57BL/6 or BALB/c mice were treated with vehicle, TNBS alone, TNBS + anti-IL-16 monoclonal antibody (mAb), TNBS + control mAb, or were untreated. Colonic injury and inflammation were evaluated after 3 or 10 days. RESULTS: Colonic IL-16 protein levels were increased in patients with Crohn's disease (P<0.05) but not ulcerative colitis. Anti-IL-16 mAb treatment significantly reduced TNBS-induced weight loss (P< 0.001), mucosal ulceration (P<0.05), myeloperoxidase activity (P< 0.001), and TNBS-mediated increases in mucosal levels of IL-1beta (P<0.05) and tumor necrosis factor alpha (P<0.01). CONCLUSIONS: Anti-IL-16 mAb reduced colonic injury and inflammation induced by TNBS in mice. Colonic mucosal IL-16 levels were elevated in Crohn's disease, suggesting a role for IL-16 in the pathophysiology of inflammatory bowel disease.
Animals↗
Gastric mucosal alpha(4)beta(7)-integrin-positive CD4 T lymphocytes and immune protection against helicobacter infection in mice.
BACKGROUND & AIMS: The integrin alpha(4)beta(7) mediates homing of effector/memory lymphocytes to the intestine and the mucosa-associated lymphoid tissue. This study examined the ability of alpha(4)beta(7)(hi) CD4(+) T lymphocytes to home to the stomach and their role in immunization-mediated protection against Helicobacter felis infection. METHODS: Gastric lamina propria and circulating mononucleated cells of naive, infected, and immunized Swiss Webster mice were isolated, and alpha(4)beta(7)-integrin expression was quantified by flow cytometry on CD4(+) T lymphocytes. Anti-alpha(4)beta(7)-integrin antibody was used to block alpha(4)beta(7) function in vivo. RESULTS: In naive mice, alpha(4)beta(7)(hi) CD4(+) T cells were enriched approximately 10-fold in the gastric mucosa compared with peripheral blood (P<0.0001). Chronic H. felis infection did not alter these proportions, but oral immunization with H. felis sonicate plus cholera toxin (CT) or with CT alone markedly increased gastric alpha(4)beta(7)(hi) CD4(+) T cells compared with naive and infected controls (P = 0.0008 and P = 0.002 for H. felis sonicate and CT, respectively). Anti-alpha(4)beta(7)-integrin antibody blocked the protection induced by oral immunization with H. felis sonicate and CT. CONCLUSIONS: The integrin alpha(4)beta(7) participates in the homing of CD4(+) T lymphocytes to the stomach and in the protection of the gastric mucosa against H. felis infection.
Administration, Oral↗
p38 MAP kinase activation by Clostridium difficile toxin A mediates monocyte necrosis, IL-8 production, and enteritis.
Clostridium difficile toxin A causes acute neutrophil infiltration and intestinal mucosal injury. In cultured cells, toxin A inactivates Rho proteins by monoglucosylation. In monocytes, toxin A induces IL-8 production and necrosis by unknown mechanisms. We investigated the role of mitogen-activated protein (MAP) kinases in these events. In THP-1 monocytic cells, toxin A activated the 3 main MAP kinase cascades within 1 to 2 minutes. Activation of p38 was sustained, whereas stimulation of extracellular signal-regulated kinases and c-Jun NH(2)-terminal kinase was transient. Rho glucosylation became evident after 15 minutes. IL-8 gene expression was reduced by 70% by the MEK inhibitor PD98059 and abrogated by the p38 inhibitor SB203580 or by overexpression of dominant-negative mutants of the p38-activating kinases MKK3 and MKK6. SB203580 also blocked monocyte necrosis and IL-1beta release caused by toxin A but not by other toxins. Finally, in mouse ileum, SB203580 prevented toxin A-induced neutrophil recruitment by 92% and villous destruction by 90%. Thus, in monocytes exposed to toxin A, MAP kinase activation appears to precede Rho glucosylation and is required for IL-8 transcription and cell necrosis. p38 MAP kinase also mediates intestinal inflammation and mucosal damage induced by toxin A.
Animals↗
Differential activation of mitogen-activated protein kinases in AGS gastric epithelial cells by cag+ and cag- Helicobacter pylori.
The aim of this study was to determine whether Helicobacter pylori activates mitogen-activated protein (MAP) kinases in gastric epithelial cells. Infection of AGS cells with an H. pylori cag+ strain rapidly (5 min) induced a dose-dependent activation of extracellular signal-regulated kinases (ERK), p38, and c-Jun N-terminal kinase (JNK) MAP kinases, as determined by Western blot analysis and in vitro kinase assay. Compared with cag+ strains, cag- clinical isolates were less potent in inducing MAP kinase, particularly JNK and p38, activation. Isogenic inactivation of the picB region of the cag pathogenicity island resulted in a similar loss of JNK and p38 MAP kinase activation. The specific MAP kinase inhibitors, PD98059 (25 microM; MAP kinase kinase (MEK-1) inhibitor) and SB203580 (10 microM; p38 inhibitor), reduced H. pylori-induced IL-8 production in AGS cells by 78 and 82%, respectively (p < 0.01 for each). Both inhibitors together completely blocked IL-8 production (p < 0.001). However, the MAP kinase inhibitors did not prevent H. pylori-induced IkappaBalpha degradation or NF-kappaB activation. Thus, H. pylori rapidly activates ERK, p38, and JNK MAP kinases in gastric epithelial cells; cag+ isolates are more potent than cag- strains in inducing MAP kinase phosphorylation and gene products of the cag pathogenicity island are required for maximal MAP kinase activation. p38 and MEK-1 activity are required for H. pylori-induced IL-8 production, but do not appear to be essential for H. pylori-induced NF-kappaB activation. Since MAP kinases regulate cell proliferation, differentiation, programmed death, stress, and inflammatory responses, activation of gastric epithelial cell MAP kinases by H. pylori cag+ strains may be instrumental in inducing gastroduodenal inflammation, ulceration, and neoplasia.
Antigens, Bacterial↗
Bovine immunoglobulin concentrate-clostridium difficile retains C difficile toxin neutralising activity after passage through the human stomach and small intestine.
BACKGROUND: Bovine immunoglobulin concentrate (BIC)-Clostridium difficile is prepared from the colostrum of cows immunised against C difficile toxins and contains high concentrations of neutralising IgG antitoxin. AIMS: To determine the proportion of BIC-C difficile which survives passage through the human stomach and small intestine. METHODS: Six volunteers with an end ileostomy took 5 g of BIC-C difficile containing 2.1 g of bovine IgG on four occasions: alone, with an antacid, during treatment with omeprazole, and within enteric coated capsules. RESULTS: When BIC-C difficile was taken alone, a mean (SEM) of 1033 (232) mg of bovine IgG was recovered in the ileal fluid representing 49% of the total ingested dose. Bovine IgG recovery was not significantly increased by antacid (636 (129) mg) or omeprazole (1052 (268) mg). The enteric capsules frequently remained intact or only partially opened in the ileal effluent and free bovine IgG levels were low in this treatment group (89 (101) mg). Bovine IgG recovery was higher in volunteers with shorter (less than two hours) mouth to ileum transit times (68% versus 36%, p<0. 05). Specific bovine IgG against C difficile toxin A was detected in ileal fluid following oral BIC. Toxin neutralising activity was also present and correlated closely with bovine IgG levels (r=0.95, p<0. 001). CONCLUSION: BIC-C difficile resists digestion in the human upper gastrointestinal tract and specific anti-C difficile toxin A binding and neutralising activity was retained. Passive oral immunotherapy with anti-C difficile BIC may be a useful non-antibiotic approach to the prevention and treatment of C difficile antibiotic associated diarrhoea and colitis.
Administration, Oral↗
Monocytic cell necrosis is mediated by potassium depletion and caspase-like proteases.
Apoptosis is a physiological cell death that culminates in mitochondrial permeability transition and the activation of caspases, a family of cysteine proteases. Necrosis, in contrast, is a pathological cell death characterized by swelling of the cytoplasm and mitochondria and rapid plasma membrane disruption. Necrotic cell death has long been opposed to apoptosis, but it now appears that both pathways involve mitochondrial permeability transition, raising the question of what mediates necrotic cell death. In this study, we investigated mechanisms that promote necrosis induced by various stimuli (Clostridium difficile toxins, Staphylococcus aureus alpha toxin, ouabain, nigericin) in THP-1 cells, a human monocytic cell line, and in monocytes. All stimuli induced typical features of necrosis and triggered protease-mediated release of interleukin-1beta (IL-1beta) and CD14 in both cell types. K+ depletion was actively implicated in necrosis because substituting K+ for Na+ in the extracellular medium prevented morphological features of necrosis and IL-1beta release. N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, a broad-spectrum caspase inhibitor, prevented morphological features of necrosis, plasma membrane destruction, loss of mitochondrial membrane potential, IL-1beta release, and CD14 shedding induced by all stimuli. Thus, in monocytic cells, necrosis is a cell death pathway mediated by passive K+ efflux and activation of caspase-like proteases.
Amino Acid Chloromethyl Ketones↗
Clostridium difficile toxin A stimulates macrophage-inflammatory protein-2 production in rat intestinal epithelial cells.
Neutrophil infiltration of the colonic mucosa is a hallmark of Clostridium difficile toxin A-mediated enterocolitis. Macrophage-inflammatory protein-2 (MIP-2) is a potent neutrophil chemoattractant secreted by rat macrophages and epithelial cells in response to inflammatory stimuli. In this work, we report that administration of toxin A into rat ileal loops increased mucosal levels of MIP-2 before the onset of fluid secretion and mucosal neutrophil infiltration. Administration of rabbit anti-MIP-2 IgG, but not control IgG, reduced toxin A-mediated secretion (by 58%), mucosal permeability (by 80%), and myeloperoxidase activity (by 85%). Immunohistochemical analysis demonstrated increased MIP-2 expression in intestinal epithelial and lamina propria cells 1 h after toxin A administration. Intestinal epithelial cells purified from toxin A-exposed ileal loops also showed increased MIP-2 mRNA expression and MIP-2 protein release that was inhibited by pretreatment of rats with the transcriptional inhibitor actinomycin D. These results indicate that C. difficile toxin A induces MIP-2 release from intestinal epithelial cells and that MIP-2 contributes to neutrophil mucosal influx during toxin A enteritis.
Animals↗
Helicobacter pylori lipopolysaccharide binds to CD14 and stimulates release of interleukin-8, epithelial neutrophil-activating peptide 78, and monocyte chemotactic protein 1 by human monocytes.
Helicobacter pylori gastritis is characterized by leukocyte infiltration of the gastric mucosa. The aims of this study were to determine whether H. pylori-derived factors stimulate chemokine release from human monocytes and to ascertain whether H. pylori lipopolysaccharide (LPS) may be responsible for this effect. Human peripheral blood monocytes were exposed to an H. pylori water extract (HPE) or to purified H. pylori LPS. Levels of the chemokines interleukin-8 (IL-8), epithelial neutrophil-activating peptide 78 (ENA-78), and monocyte chemotactic protein 1 (MCP-1) were measured by enzyme-linked immunosorbent assay. The contribution of H. pylori LPS to monocyte activation was determined by using the LPS antagonist Rhodobacter sphaeroides lipid A (RSLA) and a blocking monoclonal antibody to CD14 (60bca). HPE increased monocyte secretion of IL-8, ENA-78, and MCP-1. Heat treatment of HPE did not reduce its ability to activate monocytes. Purified H. pylori LPS also stimulated monocyte chemokine production but was 1,000-fold less potent than Salmonella minnesota lipid A. RSLA blocked H. pylori LPS-induced monocyte IL-8 release in a dose-dependent fashion (maximal inhibition 82%, P < 0.001). RSLA also inhibited HPE-induced IL-8 release (by 93%, P < 0.001). The anti-CD14 monoclonal antibody 60bca substantially inhibited IL-8 release from HPE-stimulated monocytes (by 88%, P < 0.01), whereas the nonblocking anti-CD14 monoclonal antibody did not. These experiments with potent and specific LPS inhibitors indicate that the main monocyte-stimulating factor in HPE is LPS. H. pylori LPS, acting through CD14, stimulates human monocytes to release the neutrophil-activating chemokines IL-8 and ENA-78 and the monocyte-activating chemokine MCP-1. Despite its low relative potency, H. pylori LPS may play an important role in the pathogenesis of H. pylori gastritis.
Chemokine CCL2↗
Clostridium difficile infection.
Clostridium difficile infection is associated with broad-spectrum antibiotic therapy and is the most common cause of infectious diarrhea in hospital patients. Pathogenic strains of C. difficile produce two protein exotoxins, toxin A and toxin B, which cause colonic mucosal injury and inflammation. Infection may be asymptomatic, cause mild diarrhea, or result in severe pseudomembranous colitis. Diagnosis depends on the demonstration of C. difficile toxins in the stool. The first step in management is to discontinue the antibiotic that caused diarrhea. If diarrhea and colitis are severe or persistent, oral metronidazole is the treatment of choice. Oral vancomycin is also effective, but it is more expensive than metronidazole and its widespread use may encourage the proliferation of vancomycin-resistant nosocomial bacteria. Diarrhea and colitis usually improve within three days after a patient starts taking metronidazole or vancomycin, but 20% suffer a relapse of diarrhea when these agents are discontinued.
Administration, Oral↗
Increased substance P responses in dorsal root ganglia and intestinal macrophages during Clostridium difficile toxin A enteritis in rats.
Previously we reported that pretreatment of rats with the substance P (SP) antagonist CP-96,345 inhibits the enterotoxic responses following administration of toxin A from Clostridium difficile into ileal loops, indicating that SP participates in the intestinal responses to this toxin. We now report that injection of toxin A into rat ileum causes a rapid increase in SP content in lumbar dorsal root ganglia (DRG) and mucosal scrapings 30-60 min after toxin A administration. Toxin A-mediated fluid secretion, mannitol permeability, and ileal histologic damage is significantly increased only after 2 hr. Toxin A also causes an increase in the abundance of SP mRNA in lumbar DRG and ileal mucosa as measured by reverse transcription-PCR. Lamina propria macrophages (LPMs) obtained from toxin A-injected loops release greater amounts of tumor necrosis factor alpha (TNFalpha) and SP as compared with LPMs isolated from buffer-injected loops (P < 0.01). Pretreatment of rats with the SP antagonist CP-96,345 inhibits toxin A-mediated TNFalpha release from isolated LPMs, whereas an inactive enantiomer (CP-96,344) of the SP antagonist has no effect. LPMs obtained from toxin A-injected ileal loops incubated in vitro with SP (10(-8) to 10(-9) M) show enhanced TNFalpha secretion, whereas LPMs isolated from buffer-injected loops do not respond to SP. In addition, LPMs obtained from toxin A-injected ileal loops incubated in vitro with CP-96,345 showed a diminished TNFalpha release. Our results indicate that activated LPMs secrete SP during toxin A enteritis that can lead to secretion of cytokines, suggesting an autocrine/paracrine regulation of cytokine secretion by SP from LPMs during intestinal inflammation.
Animals↗
Helicobacter pylori infection activates NF-kappa B in gastric epithelial cells.
BACKGROUND & AIMS: Helicobacter pylori adheres to gastric epithelial cells and stimulates interleukin (IL)-8 production. This may be instrumental in neutrophil infiltration of the gastric epithelium that characterizes H. pylori gastritis. This study examined the molecular mechanisms leading to H. pylori-induced epithelial cell IL-8 production. METHODS: Electrophoretic mobility shift analyses for NF-kappa B were performed on cell and nuclear extracts from H. pylori-infected AGS and Kato III human gastric epithelial cells. RESULTS: H. pylori infection activated the transcription factor NF-kappa B and induced nuclear translocation of both NF-kappa B p50/p65 heterodimers and p50 homodimers. Nuclear translocation of NF-kappa B (30 minutes) was followed by increased IL-8 messenger RNA (1 hour) and protein levels (4 hours) consistent with NF-kappa B up-regulation of IL-8 gene transcription. Pretreatment of AGS cells with PDTC, which blocks NF-kappa B activation, inhibited H. pylori-induced increases in IL-8 production by 90%. Immunohistochemical studies using a monoclonal antibody that recognizes the I-kappa B binding region of p65 showed activated NF-kappa B in gastric epithelial cells of patients with H. pylori gastritis. CONCLUSIONS: H. pylori infection activates NF-kappa B in gastric epithelial cells in vitro and in vivo. NF-kappa B is a transcriptional regulator of IL-8 production, and its activation after bacterial infection may be an important defense response in gastrointestinal epithelial cells.
Biopsy↗
Survival of anti-Clostridium difficile bovine immunoglobulin concentrate in the human gastrointestinal tract.
To be therapeutically active, oral hyperimmune bovine immunoglobulin concentrate (BIC) must survive its passage through the intestinal tract. This led us to study the gastrointestinal stability of orally administered BIC directed against Clostridium difficile toxins (BIC-C. difficile). BIC-C. difficile was stable at neutral pH in vitro but was degraded at low pH, particularly in the presence of pepsin. Healthy volunteers (n = 6) took BIC-C. difficile (45 or 8 g) as a single oral dose. Total bovine immunoglobulin G (IgG) and specific anti-C. difficile IgG were measured in the stool. BIC was given under the following conditions: in the fasting state, in the fed state, with antacid, during omeprazole therapy, or in enteric capsules (released at pH > 6). The mean fecal bovine IgG content of 3-day stool collections was similar in the fasting (536 mg; 3.8% of the ingested dose of BIC), fed (221 mg; 1.6%), and antacid (381 mg; 2.7%) groups. Omeprazole therapy was associated with increased fecal bovine IgG levels (1253 mg; 8.8%), but this difference did not reach statistical significance (P = 0.07). Administration of 8 g of BIC-C. difficile in enteric capsules resulted in substantially higher fecal bovine IgG levels (1,124 mg; 32.7% of the oral dose) than those obtained after administration of nonencapsulated BIC (22 MG; 0.6%; P = 0.004). An inverse relationship was noted between intestinal transit time and fecal bovine IgG content (R = 0.83; P = 0.04 [data from omeprazole group]). Filtrates of stool samples collected after oral administration of BIC-C. difficile neutralized the cytotoxicity of C. difficile toxins A and B, whereas control stool filtrates did not. Bovine colostral IgG undergoes partial degradation in the intestinal tract. Exposure to acidic gastric secretions and prolonged colonic transit may both contribute to IgG degradation. Nonetheless, humans taking BIC-C. difficile orally have neutralizing antitoxin activity in their stool.
Administration, Oral↗
Intravenous immunoglobulin therapy for severe Clostridium difficile colitis.
BACKGROUND: Many individuals have serum antibodies against Clostridium difficile toxins. Those with an impaired antitoxin response may be susceptible to recurrent, prolonged, or severe C difficile diarrhoea and colitis. AIMS: To examine whether treatment with intravenous immunoglobulin might be effective in patients with severe pseudomembranous colitis unresponsive to standard antimicrobial therapy. PATIENTS: Two patients with pseudomembranous colitis not responding to metronidazole and vancomycin were given normal pooled human immunoglobulin intravenously (200-300 mg/kg). METHODS: Antibodies against C difficile toxins were measured in nine immunoglobulin preparations by ELISA and by cytotoxin neutralisation assay. RESULTS: Both patients responded quickly as shown by resolution of diarrhoea, abdominal tenderness, and distension. All immunoglobulin preparations tested contained IgG against C difficile toxins A and B by ELISA and neutralised the cytotoxic activity of C difficile toxins in vitro at IgG concentrations of 0.4-1.6 mg/ml. CONCLUSION: Passive immunotherapy with intravenous immunoglobulin may be a useful addition to antibiotic therapy for severe, refractory C difficile colitis. IgG antitoxin is present in standard immunoglobulin preparations and C difficile toxin neutralising activity is evident at IgG concentrations which are readily achieved in the serum by intravenous immunoglobulin administration.
Antibodies↗
Enterocytes are the primary source of the chemokine ENA-78 in normal colon and ulcerative colitis.
Epithelial cell-derived neutrophil-activating protein-78 (ENA-78) is a neutrophil-directed C-X-C chemokine. We report that Caco-2 and T84 human intestinal epithelial cells produce ENA-78 after stimulation by interleukin (IL)-1 beta or tumor necrosis factor-alpha. Caco-2 cells show increased IL-8 production at 4-12 h and increased ENA-78 production at 8-24 h after cytokine stimulation. Immunohistochemical studies in normal human colon and in ulcerative colitis demonstrate ENA-78 immunoreactivity principally associated with crypt epithelial cells. Furthermore, human colonic tissues from patients with ulcerative colitis show elevated levels of ENA-78 mRNA (24-fold increase, P < 0.01) and protein (4-fold increase, P < 0.05) compared with normal controls. Thus ENA-78 is produced in normal colon and in ulcerative colitis and is predominantly of enterocyte origin. The kinetics of ENA-78 induction in human colon epithelial cell lines are delayed and prolonged compared with IL-8. We propose that ENA-78 and IL-8 serve complementary and sequential roles in neutrophil recruitment in ulcerative colitis. ENA-78 as an enterocyte-derived, neutrophil-activating chemokine may be especially important in neutrophil recruitment from the lamina propria into the epithelial layer.
Cell Line↗
IL-11 inhibits Clostridium difficile toxin A enterotoxicity in rat ileum.
Interleukin-11 (IL-11) is a stromal cell-derived cytokine with several biological activities against hematopoietic cells. Recent results indicated that IL-11 reduced mucosal damage in animal models of colitis. This study aimed to explore the action of recombinant human IL-11 (rhIL-11) on the intestinal effects of Clostridium difficile toxin A, an inflammatory enterotoxin, and cholera toxin, a noninflammatory enterotoxin in rat ileum. We administered rhIL-11 subcutaneously to rats before injection of toxin A into ileal loops and measured fluid secretion, epithelial permeability to mannitol, histopathological damage, and release of rat mast cell protease II (RMCP II) from intestinal mast cells and of tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-2 (MIP-2) from lamina propria macrophages. rhIL-11 (50-1,000 micrograms/kg) inhibited toxin A but not cholera toxin-mediated secretion and permeability in a dose-dependent fashion and reduced toxin A-induced epithelial cell damage. Rats treated with rhIL-11 also showed reduced RMCP II, TNF-alpha, and MIP-2 release in response to toxin A. Exposure of rat peripheral monocytes in vitro to rhIL-11 (1 microgram/ml) inhibited lipopolysaccharide and toxin A-mediated increases in TNF-alpha mRNA and protein levels. We conclude that rhIL-11 blocks the intestinal effects of C. difficile toxin A, possibly by inhibiting release of inflammatory mediators from mucosal mast cells and intestinal macrophages.
Animals↗
IL-8 release and neutrophil activation by Clostridium difficile toxin-exposed human monocytes.
Neutrophil infiltration is central to the pathogenesis of Clostridium difficile toxin A-induced enterocolitis. This study examines whether monocyte activation by C. difficile toxins is instrumental in initiating neutrophil activation and recruitment. Human monocytes were exposed to low concentrations of highly purified C. difficile toxins, and the conditioned media were harvested for cytokine and functional assays. Monocytes exposed to C. difficile toxin A (10(-10) M) or toxin B (10(-12) M) released 100 and 20 times basal levels, respectively, of the neutrophil chemoattractant interleukin-8 (IL-8). Reverse transcriptase-polymerase chain reaction demonstrated a marked increase in IL-8 mRNA expression by monocytes 3 h after toxin exposure. Conditioned media from toxin A- and toxin B-treated monocytes stimulated neutrophil migration (324 and 245% of control, respectively). This effect was completely blocked by IL-8 antiserum. These media also upregulated neutrophil CD11b/CD18 and endothelial cell intercellular adhesion molecule-1 expression. C. difficile toxins, at low concentrations, potently activate monocytes to release factors, including IL-8, that facilitate neutrophil extravasation and tissue infiltration. Our findings indicate a major role for toxin-mediated monocyte and macrophage activation in C. difficile colitis.
Bacterial Proteins↗